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Morphological Taxonomy of Black Pepper (Piper nigrum) Leaf Gall Thrips in Sri Lanka
C.U. Widanapathirana1, M.R. Ulitzka2, S.A. Yap3
1National Cinnamon Research and Training Centre, Department of Export Agriculture,
Thihagoda, Sri Lanka, chinthakauw@gmail.com
2Straßburger Straße 37A, 77652 Offenburg, Germany
3Institute of Weed Science Entomology and Plant Pathology, University of Philippines Los
Banos, Philippines
ABSTRACT
In India and Sri Lanka, Leaf Gall Thrips(LGT) is considered among major pests of Black pepper
(Piper nigrum). LGTs initially infest tender leaves causing tubular and hypophyllous galls
along the leaf margin.Gynaikothrips karnyi was first recorded by Bagnall (1914) from Sri Lanka
and subsequently by Ananthakrishnan(1952) in India. However, Tillakeratne et al(2012),
identified only two species of Gynaikothrips in their extensive survey in 2005 - 2008, in which,
G. karnyi is not included. In their checklist, Liothrips karnyi was mentioned to be infesting
Piper nigrum L, forming leaf galls. Devasahayam(1994) mentions three species of thrips
infesting the pepper leaf in India but G. karnyi has not been identified as a leaf gall forming
species in pepper.This leads to a serious taxonomic confusion where the precise identification
of the LGTs in pepper in Sri Lanka is debated. Therefore, the present study was intended to
correctly identify the pepper LGTs in Sri Lanka through morphological examination.Live
specimens of pepper thrips were collected from 5 districts and taxonomically
investigated.Abdominal segment X is tubelike, forewing surface free of microtrichia,Maxillary
stylets narrow,distance between midcoxae is broader than of hind coxae, abdominal segment
IX shorter, forewings not banded,abdominal tergite with two pairs of wing retaining setae,
cheeks without warts, forewing has parallel sides, maxillary bridge absent, stylets are retracted
in to posterior margin of compound eyes, pronotum with five pairs of distinct setae, sculpture
indistinct, both sexes lack fortarsal tooth. Mid and hind tibiae are yellowish in colour and
antennal segments VII and VIII are uniformly pale as V and VI. These characteristic features
lead the specimens to Liothrips mirabilis (Schumtz) belonging to Family Phlaeothripidae,
Suborder Tubulifera, Subfamily Phlaeothripinae. This result updates the existing Thysanoptera
checklist of Sri Lanka,confirming the confusing original description of L. mirabilis by
Priesner(1968).
Key words : Black pepper, Piper nigrum, Leaf Gall Thrips, Liothrips mirabilis, Gynaikothrips
karnyi,
Introduction
Black pepper (Piper nigrum) is a perennial flowering plant that belongs to the plant family
Piperaceae. Being one of the most widely used spices in the world, it is known as the King of
Spices. Infestation by insect pests is a main factor responsible for the low productivity of pepper
in major pepper growing countries. In India and Sri Lanka, Leaf Gall Thrips (LGT) is
considered among major pests of pepper (Ravindran, 2000). LGTs initially infest tender leaves
resulting the margins curling inwards, causing tubular and hypophyllous galls along the leaf
margin (Fig 1.0 A) The attacked leaves become undersized and pale, as the growth of the
attacked veins gets arrested (Ravindran, 2000).
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Fig 1.0 Pepper Leaf Gall Thrips A - Damage on Pepper Leaves B - Adult Thrips C - Nymph of
Pepper Thrips
Devasahayam (1994) mentioned three species of thrips (Order Thysanoptera) infesting the
pepper leaf in India : Liothrips chavicae Z., L. karnyi Bagn. and L. pallipes Karny. Sarma Y.R
et al (1987) referred to this pest as marginal gall-forming thrips - Liothrips karnyi (Fig 1.0 B).
Visalakshi and Joseph (1966) stated that LGT, Gynaikothrips karnyi was first recorded by
Bagnall (1914) from Sri Lanka and subsequently by Ananthakrishnan (1952) in India.
However, according to Tillekaratne et al (2011), only two species of Gynaikothrips have been
identified in their survey for thrips in Sri Lanka in 2005 - 2008, none of which is making galls
on pepper leaves. In their checklist, Liothrips karnyi (Bagnall 1914) has been mentioned to be
infesting Piper nigrum L, forming leaf galls.
This leads to a serious taxonomic confusion where the precise identification of the Gall forming
thrips in black pepper in Sri Lanka is debated. Therefore, the present study was intended to
correctly identify the Leaf Gall Thrips (LGT) in Sri Lanka through standard morphological
taxonomic methods and record its identity, updating the country’s existing thrips checklist.
Materials and Methods
Live specimens of pepper thrips were collected from hand-picked pepper leaves selected from
5 districts of Sri Lanka at the National Cinnamon Research and Training (NCRTC), Department
of Export Agriculture, Thihagoda. The marginal leaf galls were carefully cut and opened to
remove the adult pepper gall thrips and they were kept in the 5% NaOH liquid for the body
contents to be cleared. Then the slides were prepared in Hoyer’s media and mainly using
standard and published morphological taxonomic keys provided by Mound, L.A. (2020) and
Mound and Kibby (1998), they were subjected to taxonomic identification. Results were
confirmed by Dr. Manfred R. Ulitzka, Research Entomologist, Offenburg, Germany.
Results and Discussion
Liothrips Uzel, 1895 is the largest genus in the subfamily Phlaeothripinae, comprising 283
named species. However, species identification in this genus is very difficult and only available
identification key (Priesner 1953) is unreliable and misleading (Mound,2020).
The original description of L. mirabilis is confusing as it is stated to have been taken by Uzel
on the leaves of Pavetta hispida and rolled leaf of a pepper plant in Peradeniya, Sri Lanka in
1902. Priesner in 1968 studied one specimen from the type series but could not say which plant
it came from. He also did not study the original specimens of karnyi collected at Peradeniya in
1913, from pepper. He therefore placed karnyi twice in his key, providing opportunity for
uncertainty. Liothrips karnyi and Liothrips mirabilis have the same unusual character state of
A
B
C
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antennal segments VII and VIII as pale as V and VI thus it has been considered that they are a
single species, known only from type specimens taken in Sri Lanka (Mound, 2020).
Abdominal segment X is tubelike (Fig 2.0 – A), forewing surface is free of microtrichia which
is a characteristic feature of Family Phlaeothripidae, Suborder Tubulifera. Maxillary stylets are
narrow as of Sub family Phlaeothripinae, distance between midcoxae is broader compared to
that is of hind coxae, abdominal segment IX and tube are shorter, macropterous, forewings not
banded, each abdominal tergite with two pairs of wing retaining setae, Male has no large
tubercle on the inner margin of femur near base (Fig 2.0 – C) cheeks without warts, forewing
has parallel sides (Fig 2.0 – B), maxillary bridge absent, and stylets are retracted in to the back
margin of compound eyes, pronotum with five pairs of well-developed distinct setae, sculpture
indistinct, both sexes lack foretarsal tooth. These characteristic features lead the specimens to
the genus liothrips. Mid and hind tibiae are yellowish in colour (Fig 2.0 – B)and antennal
segments VII and VIII are uniformly pale as V and VI (Fig 2.0 – C) as described for Liothrips
mirabilis.
Figure 2.0 Pepper Leaf Gall Thrips (L. mirabilis) A - L. mirabilis B – Mid and hind
tibia with fore wing, C – Antenna of L. mirabilis
Conclusion
This study taxonomically re-identifies the pepper leaf gall thrips as Liothrips mirabilis based
on the latest taxonomic classification and updates the thrips checklist in Sri Lanka, resolving
the historical taxonomic confusion on this species.
Reference
1. Devasahayam, S. and Koya, K.M.A. (1994) Natural enemies of Major insect pests of black
pepper (Piper nigrum L.) in India, journal of Spices and Aromatic Crops 3(1), 1994, 50 – 55
2. Mound, L.A. (2020) Liothrips species (Thysanoptera, Phlaeothripinae) from leaf-galls on
Piper species in Southeast Asia and Australia, Zootaxa, 4830 (2): 383–391
3. Mound, L.A. & Kibby, G. (1998) Thysanoptera: An Identification Guide, 2nd Ed., CAB
International, UK, ISBN 0851992110, pp 70
4. Ravindran, P.N. (2000) Black Pepper : Piper nigrum, CRS Press, Harwood academic
publishers, pp 527
5. Tillekaratne, K., Edirisinghe, J.P., Gunatilleke, C.V.S. and Karunaratne, W.A.I.P (2011),
Survey of thrips in Sri Lanka: A checklist of thrips species, their distribution and host plants,
Ceylon Journal of Science (Bio. Sci.) 40 (2): 89-108
6. Visalakshi, A. and Joseph, K.V. (1966) Biology of Gynaikothrips karnyi Bagnall,
the marginal gall forming thrips of Pepper, Agricultural Research Journal of Kerala, Dec 6
(1966), 1 - 4
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B
C
